The conventional techniques carried out by dentists to obtain an adequate occlusal morphology in a particular tooth require the use of burs manufactured in different sizes and materials and in conjunction with rotary instruments, trimming, contouring and polishing are carried out. This is very time consuming and very rarely the operator can reproduce the initial morphology of the tooth accurately, that is, the morphology of the tooth before treatment (cavity preparation) is difficult to be reproduced with precision and some enamel and restorative material can also be accidentally eliminated during the contouring and trimming process.
Elimination of either restorative material or enamel during the contouring and trimming process inevitably leads to the development of incorrect and deficient contact points between the upper and lower teeth. Consequently, overeruption of the opposite tooth may occur and this will cause an occlusal discrepancy which will create discomfort to the patient.
During the trimming and contouring process, some defects may be created at the junction of the restorative material and tooth surface. In these defects, a bacterial population may develop and proliferate more easily and thus failure of the restoration will occur.
The procedures used to repair the damaged occlusal morphology of a tooth are various. For example, pre-fabricated molds or matrices which simulate a defined standard anatomy and made of different materials can be applied on the tooth. The occlusal anatomy of such tooth, however, can never be accurately reproduced with a non-customized device. The operator is forced to carry out the conventional contouring routine anyway to adapt the mold to each tooth individually. An example of this is the preformed occlusal `forms` developed for composite fillings or other restorative materials.
An other way to avoid the formation bulges, and bulky edges of restorative material on the margins of the cavity is the `shaping bite procedure` proposed by Fusayama and described in the Revista Odontoestomatologica Espanola N.degree. 441, March 1992, page 45, in which the patient actually `bites` directly onto the still soft restorative material.
Other authors use devices to register the occlusal morphology such as a wooden surface or sheet or similar in conjunction with an opaque impression material. This kind of impression material requires the use of a separating medium to prevent it from adhering to the hardened restorative material. This procedure does not achieve the rigidity and transparency needed for the desired application.
Occlusal conformation systems by mean of complex computers programs (CAD-CAM) reproduce the anatomy of a tooth extrapolating an optic readout before cavity preparation and obtaining a virtual anatomy with great accuracy, manufacturing the final restoration with a robotic cavity preparation system. Even though the fit or adjustment of the final restoration is quite accurate, the occlusal morphology due to the fact that is limited to the use of ceramic materials in a bulk, inserted and cemented in the tooth after its finishing.
The use of impression materials to reproduce the occlusal surface anatomy of teeth is well known by the majority of them are opaque and are taken to the mouth with devices with the shape of an arch (stocks trays) that although rigid, are designed to obtain the mold of the complete dental arch containing teeth and gums, as well as the relationship between upper and lower arches (bit). These trays are often constructed in opaque materials or colored translucid materials (plastic) but the latter can often be subject to deformation when heat is applied to them.